a) Field of the Invention:
The present invention relates to electronic locking, especially to an optical theft deterrent system capable of optically providing a key code for authorized operation of a driven device.
b) Description of the prior art:
Since a U.S. patent was granted in 1848 to Linus Yale Sr. the inventor of a cylinder lock device, many types of mechanical cylinder lock devices have been utilized in buildings, automotive vehicles or other objects to prevent unauthorized access or use thereof. In another aspect, various types of electrically operated locking devices have been developed including keyless entry system and infra-red unlocking apparatus.
For example, Japanese Patent Disclosure No. 62-173354 exhibits an anti-theft device which comprises a combination of mechanical and electronic locking devices. The electronic locking device may be unlocked upon receiving an infra-red ray including a specific key coded optical signal emitted from a key. Specifically, an electric circuit mounted on the key comprises means for producing the coded optical signal, and the locking device comprises identifying means for producing a trigger signal to unlock a locking apparatus upon receiving the coded optical signal emitted from the key. In this combined mechanical and electronic locking structure, the anti-theft device can not be unlocked unless mechanically operated by a proper key in addition to the electric trigger signal resulted from the coded optical signal. As the device further comprises output means for detecting "picking", if the anti-theft device is unlocked only by mechanical operation without the trigger signal of the identifying means to be generated upon receiving the optical signal, it produces a "picking" detecting signal in order to drive a warning device. The term "picking" is used to mean the unauthorized unlocking of a mechanical locking device by means of a specific tool. In this tamper-proof structure, if the identifying means generates the trigger signal after the device has received the specific coded optical signal emitted from the key and simultaneously the device is mechanically unlocked, the warning device can not be activated.
Then, Japanese Patent Publication No. 62-174476 discloses an electronic control apparatus for buildings and automobiles which comprises an electronic key for generating light signals of predetermined coded signals; identifying means for producing a trigger signal upon receiving the matching light signals; and a lock mechanism actuated by the trigger signal from the identifying means. This electronic control apparatus further comprises a battery; switching means; a switching circuit connected to the battery and switching means; coded signal generating means activated by output of the switching circuit; and a light source element for generating specific coded light signals in accordace with outputs of the coded signal generating means. The light signals emitted from the light source element are received by a photosensor connected to the identifying means which consequently provides an output to actuate the lock mechanism when the signals received by the photosensor match predetermined coded signals.
Also, Japanese Patent Publication No. 56-11032 exhibits a lock device which comprises a lock mechanism for electrically operating a lock actuator; and a key device provided with a transmitter. Provided in each of the lock and key devices is a pulse pattern generator which generates a specific array of pulses in synchronized relation to serial clock signals generated in an oscilator of the key device. The lock and key devices are connected through the light transmitter so that the lock actuator of the lock mechanism is operated for unlocking when the array of pulses produced in the key device coincides with that produced in the lock device.
In addition, U.S. Pat. No. 4,258,352 shows a device for controlling a lock for an automotive vehicle which comprises a transmitter independent of the vehicle and a receiver fast with the vehicle. The transmitter includes a direct current electric supply source, a coded message generator and an emitter for transmitting the message away in series. The receiver includes a battery, a detector for receiving the message from the transmitter, a memory for storing only a coded message, and a comparator for comparing the messages received by the detector and stored by the memory and producing a signal when these messages are identical. The emitter of the transmitter has a diode capable of producing infra-red radiation, and the detector of the receiver has a photodiode.
As above-mentioned, prior art optical transmitters requires a complicated electronic circuit including a battery, a coded pulse generator, an emitter and so on, and therefore these electronic parts make it difficult to mount the transmitter on a small key. Also, the complicated electronic structure results in increased processes and cost for manufacture of the transmitter. In addition, no change of the coded signals can be made by storing new ones in prior art transmitters.